1. Technical Field
The technical field is data processing, or, more specifically, methods, apparatus, and products for dynamically calibrating the offset of a receiver with a Decision Feedback Equalizer (‘DFE’) while performing data transport operations.
2. Description of Related Art
Serial chip-to-chip communications at very high speed data rates can be limited by channel loss and intersymbol interference that arises from the physical characteristics of the data communications channel. An effective way for equalizing channel loss and negating the impact of intersymbol interference is to use a high performance DFE in the receiver. A receiver with a DFE can have many high speed receiving data paths. Due to the complexity of the high performance data paths, an offset voltage may be introduced at each of the receiving data paths, thereby causing the voltage level of an incoming data signal to be skewed. Such an offset voltage can be accumulated to a high level and can impact the performance of the linear data path by causing eye closure of the incoming data at a sample latch.
The magnitude of the offset voltage at the input of a particular sample latch in a data path may be different than the magnitude of the offset voltage at the input of sample latches in other data paths. To ensure proper sampling of incoming data signals, the offset voltage at the input of each sample latch must be removed, thereby opening the incoming data eye for each data path individually. Although a receiver with a DFE can have many high speed data paths for receiving and processing an incoming signal, some portion of the each data path may be shared. The shared portion of each data path can also experience the introduction of an offset voltage that may be accumulated to a high level. This offset voltage in the shared portion of each data path must also be removed. The magnitude of each offset voltage is time variant such that the magnitude of each offset voltage may change over time, creating the need for continual calibration.